1. Field of the Invention
The present invention relates to an ink-jet recording head that performs recording by discharging a recording liquid, such as ink or the like, onto a recording medium, and an ink-jet recording apparatus including the same. More particularly, the invention relates to a flexible-film wire substrate which is used by being bent in such a recording head.
2. Description of the Related Art
Ink-jet recording apparatuses adopt a so-called non-impact recording method, and have the features that high-speed recording and recording for various recording media can be performed, and less noise is produced during recording. Accordingly, ink-jet recording apparatuses are widely adopted as printers, or recording mechanisms for word processors, facsimile apparatuses, copiers and the like.
In a typical ink-jet recording method, recording is performed on a recording medium, such as paper or the like, by discharging liquid droplets from fine discharge ports using electrothermal transducers. Such ink-jet recording is usually performed using an ink-jet recording head having nozzles for forming liquid droplets, and a supply system for supplying the head with a recording liquid, such as ink or the like.
In ink-jet recording heads using electrothermal transducers, electrothermal transducers are provided within a pressure chamber. Thermal energy is supplied to a recording liquid by providing electric pulses, serving as a recording signal, and the pressure of each generated bubble (due to film boiling) of the recording liquid caused by a phase change of the recording liquid at that time is utilized for discharging a liquid droplet for recording. Such ink-jet recording heads using electrothermal transducers utilize two methods, i.e., a method in which a recording liquid is discharged in parallel to a substrate on which electrothermal transducers are arranged (an edge shooter method), and a method in which a recording liquid is discharged perpendicularly to a substrate on which electrothermal transducers are arranged (a side shooter method).
As a result of recent tendency of reduction in the size, realization of a high speed, multicolor printing and high picture quality of ink-jet recording heads, a plurality of recording-element substrates are provided on one ink supply/holding member with an interval of several millimeters to several tens of millimeters, and very precise bonding and fixing with an interval of several micrometers to several tens of micrometers are being performed. FIG. 11 illustrates the configuration of a conventional ink-jet recording head unit. FIG. 12 illustrates a recording-element substrate 1100 in detail.
In FIG. 12, a plurality of discharge ports 1108 for discharging ink are opened in the recording-element substrate 1100, and an ink supply port 1109 for supplying ink is opened at the back of the discharge ports 1108 at a length substantially equal to the length of the string of the discharge ports 1108. The plurality of discharge ports 1108 are disposed so as to correspond to electrothermal transducers 1103 formed on a substrate 1101. Although in FIG. 12, only several discharge ports 1108 are illustrated, several tens to several hundreds of discharge ports 1108 are opened in actual products.
In order to discharge ink, electrodes on the recording-element substrate 1100 are electrically connected to electrode terminals on a flexible-film wire substrate 2 shown in FIG. 11, and an electric signal for discharging ink from the discharge ports 1108 is supplied from output terminals of the flexible-film wire substrate 2. Input terminals 204 on the flexible-film wire substrate 2 are electrically connected to output terminals of a wire substrate 5 having external input pads 7 for supplying the ink-jet recording head with an electric signal representing recording information or the like from the main body of the recording apparatus.
As shown in FIG. 11, the flexible-film wire substrate 2 to which the recording-element substrate 1100 is electrically connected is bonded and fixed on an ink supply/holding member 4.
A wire connection portion (input terminal portion) of the flexible-film wire substrate 2 includes signal-line input terminals 204 where relatively small currents flow, and power-supply-line input terminals to be connected to a power supply, ground and the like, for supplying a recording liquid with thermal energy. A wire connection portion (output terminal portion) of the wire substrate 5 includes signal-line output terminals and power-supply-line output terminals corresponding to the signal-line input terminals and the power-supply-line input terminals, respectively. The input terminals of the flexible-film wire substrate 2 and the output terminals of the wire substrates 5, whose number is several tens to several hundreds, are electrically connected at a pitch of 100-500 xcexcm.
By bending the flexible-film wire substrate 2 so as to provide two crest portions and a valley portion between these crest portions, it is possible to bend the flexible-film wire substrate 2 for a recording head 1001 along the ink supply/holding member 4, and dispose a sheet pressing roller near the recording-element substrate 1100 while preventing interference between the wire substrate 5 and the sheet pressing roller, thereby reducing the size of the apparatus (see Japanese Patent Application Laid-Open (Kokai) No. 2001-063053 (2001)).
However, the above-described ink-jet recording head has the following problems.
In the wire connection portion of the wire substrate 5, in contrast to the signal-line connection terminals where relatively small currents flow, each of the power-supply-line connection terminals to be connected to the power supply, ground and the like, for providing the recording liquid with thermal energy comprises a plurality of connection terminals in order to reduce connection resistance. Accordingly, the number of terminals at the wire connection portion of the flexible-film wire substrate 2 increases by an amount of providing a plurality of terminals corresponding to the power-supply-line connection terminals, resulting in an increase in the width of the entire wire connection portion. Furthermore, as a result of recent tendency of a high speed and high picture quality of the ink-jet recording head, the number of nozzles and the number of electrothermal transducers also increase, resulting in an increase in the number of power-supply lines for the power supply, ground and the like, provided on the flexible-film wire substrate 2.
As a result of such an increase in the number of the power-supply lines for the power supply, ground and the like, provided on the flexible-film wire substrate 2, the width of the entire flexible-film wire substrate 2 also increases. Such an increase in the width of the flexible-film wire substrate 2 has been a problem for reducing the size of the ink-jet recording head.
However, if it is intended to reduce the width of the flexible-film wire substrate 2, the width W of each connection terminal for the power-supply lines for the power supply, ground and the like is also reduced, thereby causing the problems that, when electrically connecting the terminal connection portion (the connection portion of input terminals) of the flexible-film wire substrate 2 to the terminal connection portion (the connection portion of output terminals) of the wire substrate 5, open circuit or short circuit between terminals may occur, resulting in degradation in reliability.
A structure of the flexible-film wire substrate 2 for securing reliability of terminal connection portions without sacrificing reduction in the size of the head may be considered, in which the width of portions other than terminal connection portions of the flexible-film wire substrate 2 is small while sufficiently maintaining the width of terminal connection portions.
In such a flexible-film wire substrate 2 in which the width of the terminal connection portion to be connected to the wire substrate 5 is larger than the width of other portions, when forming a wire pattern from a narrow region to a wide region, in order to make the interval between wires of the wire pattern at the wide region larger than at the narrow region, the wire pattern has an oblique portion from the narrow region to the wide region (see FIG. 9).
When, as shown in FIG. 11, disposing the external input pads 7 of the wire substrate 5 and the recording-element substrate 1100 on different surfaces of the ink supply/holding member 4, the flexible-film wire substrate 2 for electrically connecting the wire substrate 5 to the recording-element substrate 1100 is bent.
In order to realize a small-size head and prevent an increase in the wire resistance in the wire pattern, it is necessary to minimize the length of the wire pattern as well as the length of the flexible-film wire substrate 2. For that purpose, it is necessary to provide a valley portion near a portion where the wire pattern between the narrow portion and the wide portion of the flexible-film wire substrate 2 is oblique (having a tapered shape).
In such a case, however, if it is intended to bend the flexible-film wire substrate 2 at a tapered portion shown in FIG. 9, the bending property is inferior because the wire pattern is not perpendicular to a bent portion 5B, thereby causing a problem in the production process. Even if the flexible-film wire substrate 2 happens to be bent, since the flexible wire pattern tends to be bent around a line perpendicular to the wire pattern, the flexible wire pattern is bent in a sagged state, thereby causing pronounced projections and recesses on the flexible wire pattern. As a result, when mounting the recording head cartridge in a carriage of the apparatus main body, the projections and recesses on the flexible wire pattern interfere with the carriage.
The present invention has been made in consideration of the above-described problems.
It is an object of the present invention to provide a configuration allowing to excellently bend a flexible-film wire substrate without influencing a wire pattern on the substrate, in an ink-jet recording apparatus having the flexible-film wire substrate, whose width at a terminal connection portion is larger than in other portions, having a wire pattern formed from a narrow region to a wide region thereon, and bent in a predetermined state.
According to one aspect of the present invention, in an ink-jet recording head including a flexible-film wire substrate, a recording-element substrate, including energy generation elements for generating energy for discharging a recording liquid. The recording-element substrate is electrically connected to the flexible-film wire substrate. The recording head also includes a wire substrate where a signal for controlling generation of the energy on the recording-element substrate is input from an external apparatus. The wire substrate is electrically connected to the recording-element substrate via a plurality of wires formed on the flexible-film wire substrate. The flexible-film wire substrate is bent so as to provide a first crest portion near the recording-element substrate, a second crest portion near the wire substrate, and a valley portion positioned between the first crest portion and the second crest portion. A bent portion of each of the first crest portion and the second crest portion is substantially linear over the entire region. The plurality of wires are bent so that a pitch increases from the valley portion to the second crest portion on the flexible-film wire substrate at least between the valley portion and the second crest portion. The plurality of wires are substantially orthogonal to respective bent portions of the first crest portion, the second crest portion and the valley portion.
According to this configuration, in the ink-jet recording head of the present invention, by increasing the width of the flexible-film wire substrate without increasing the size of the recording head, the width W of connection terminals for power-supply lines to be connected to a power supply, ground and the like is also increased. As a result, it is possible to improve in reliability in electric connection between a terminal connection portion (a connection portion of input terminals) of the flexible-film wire substrate and a terminal connection portion (a connection portion of output terminals) of the wire substrate, and prevent break of wires while excellently maintaining the bending property of the flexible-film wire substrate.
In the ink-jet recording head of the invention, a width of the flexible-film wire substrate at the second crest portion may be larger than a width at the first crest portion.
It is preferable that the bent portion of the valley portion is substantially linear at least near a central portion of the valley portion. It is thereby possible to suppress generation of projections and recesses conforming to the shape of wires on the flexible-film wire substrate, and prevent the flexible-film wire substrate from interfering with a sheet pressing roller or a carriage. In this case, it is more preferable that the bent portion of the valley portion is substantially linear over the entire region.
According to another aspect of the present invention, an ink-jet recording apparatus includes the above-described ink-jet recording head, a carriage for mounting the ink-jet recording head, and conveyance means for conveying a recording medium. The ink-jet recording apparatus performs recording by causing the recording liquid discharged from the ink-jet recording head to adhere onto the recording medium. The conveyance means is positioned near the valley portion of the ink-jet recording head. According to this configuration, in the ink-jet recording apparatus of the present invention, reduction in the size of the apparatus is achieved by disposing the sheet pressing roller near the recording-element substrate while preventing interference between the flexible-film wire substrate and the sheet pressing roller.
As described above, according to the present invention, in the ink-jet recording head having the flexible-film wire substrate, whose width at a terminal connection portion is larger than in other portions, having a wire pattern formed from a narrow region to a wide region thereon, and bent so as to provide two crest portions and a valley portion between the two crest portions, a bent portion of each of the crest portions and the valley portion and the wire pattern on the flexible substrate are substantially orthogonal, and particularly, the wire pattern near the bent portion of the valley portion positioned at a portion where the width of the substrate widens is perpendicular to the bending line, so that the flexible substrate can be bent with producing little projections and recesses. Accordingly, when mounting the ink-jet recording head having the flexible-film wire substrate in the printer main body, the flexible-film wire substrate does not interfere with the sheet pressing roller and the like of the printer main body. Furthermore, since the sheet pressing roller near the printer main body can be disposed near the recording-element substrate while preventing interference between the flexible-film wire substrate and the sheet pressing roller by the valley portion of the flexible-film wire substrate, the size of the ink-jet recording apparatus can be reduced.